In one embodiment, a method includes receiving treatment information relating to a treatment plan for proton- or ion-beam therapy intended to irradiate a target tissue； receiving machine-limitation information relating to one or more limitations of one or more machines involved in the proton- or ion-beam therapy； determining a time-optimized beam current for a proton or ion beam based on the treatment information and the machine-limitation information, wherein the time-optimized beam current minimizes the time required to deliver a required quantity of monitor units to one of a plurality of spots, wherein each of the plurality of spots is a particular area of the target tissue； and delivering the time-optimized beam current to the particular area.
